Foam materials are commonly used for packaging. The foam is generally generated by mixing two chemical components, which expand and harden within about 10-30 seconds. In many cases, a foam dispensing gun is used to generate the foam at the packaging site. The foam is generally mixed within the dispensing gun and is ejected from the gun into a bag or a package before the foam hardens.
U.S. Pat. No. 3,178,157 to Cole, U.S. Pat. No. 6,691,898 to Hurray et al., and U.S. Pat. No. 5,462,204 to Finn, the disclosures of which are incorporated herein by reference, describe such dispensing guns used in forming the foam.
As foam materials harden within a short time, remnants of the foam may harden within the dispensing apparatus and clog flow passageways.
One solution to the clogging of passages is to include a solvent flushing path in the gun, which provides a solvent that cleans out portions of the gun that require cleaning, after every use. U.S. Pat. No. 4,262,847 to Stitzer et al., the disclosure of which is incorporated herein by reference, describes one such gun. Other dispensing guns include a mechanical cleaning device that passes through the mixing chamber between uses.
U.S. Pat. No. 5,405,083 to Moses, the disclosure of which is incorporated herein by reference, describes another dispensing gun in which a disposable mixing tube is replaced, each time the gun is used.
U.S. Pat. No. 5,429,308 to Brown, the disclosure of which is incorporated herein by reference, describes a mixing gun having a replaceable nozzle including a mixing chamber. Those parts of the gun that come in contact with the mixed chemicals are included in the replaceable nozzle. In the non-disposable part of the gun, respective valves are used to control the flow of each of the chemical components into the mixing chamber.
U.S. Pat. No. 6,375,096 to Rashidi, the disclosure of which is incorporated herein by reference, describes a foam gun with a disposable nozzle attachment including a mixing chamber in which the chemicals mix. The disposable nozzle includes one way valves for each of the chemicals entering the nozzle attachment, so as to prevent backflow of the chemicals into the non-disposable part of the gun.
The cost of the disposable nozzle attachments is not negligible and their replacement is time consuming. It is therefore desired to reduce and even eliminate the need for replacement of the disposable nozzle attachments, without incurring the costs and inconvenience involved in a solvent flushing system or a mechanical cleaning system.
U.S. Pat. No. 4,262,848 to Chabria, the disclosure of which is incorporated herein by reference, describes a dispensing gun, which does not have a mixing chamber at all. The chemicals are mixed a short distance distal from the dispensing gun. Such mixing in the air, may result in a reduced quality of the foam. A flexible extension is suggested to be used to separately lead the chemicals before they are mixed to a location forward of the gun.